The present invention relates to automatic gain control that makes constant the output signal level via gain control using the closed loop, and in particular to an automatic gain controller and an automatic gain control method wherein automatic gain control of a plurality of input signals is performed and to radio communications apparatus equipped with the automatic gain control function.
Conventionally, in some types of signal processors, for example radio communications apparatus, automatic gain control is performed in order to make constant the variation in the signal level of a received signal caused by variation of receiving field strength in a radio propagation path such as a radio circuit and to reduce demodulation errors. As such gain control signal systems are known an open loop control signal whereby the gain of a variable gain amplifier in the subsequent stage is controlled via an automatic gain control signal generated by detecting the level variation in an input signal, and a closed loop control system whereby the gain of a variable gain amplifier in the preceding stage is controlled via the automatic gain control signal.
FIG. 11 shows an example of configuration of an automatic gain controller according to the related art applied to the receiving system of radio communications apparatus. The automatic gain controller is composed of a variable gain amplifier 111, a demodulator 112, an A/D converter 113, a level detector 114, a gain control signal generator 115, and a D/A converter 116.
In the automatic gain controller according to the related art, a received signal input Ri is amplified by the variable gain amplifier 111, demodulated by the demodulator 112, and converted to a digital value by the A/D converter 113, then output as a demodulated output Rd. Part of the demodulated output Rd is level-detected by the level detector 114 and captured by an automatic gain control loop, to generate an gain control signal via the gain control signal generator 115 based on the value of the demodulated output Rd. This automatic gain control signal is converted to an analog voltage by the D/A converter 116 and fed back to the control input end of the variable gain amplifier 111 as a gain control voltage and undergoes automatic gain control via the closed loop.
In the gain control signal generator 115, the value of the demodulated output Rd (output value) level-detected by the level detector 114 is averaged by an averaging section 121 for a certain time, and the difference from a predetermined target value A is calculated in a convergence difference calculating adder 122. In a loop gain control multiplier 123, the loop gain control value B in the automatic gain controller is multiplied in a loop gain control multiplier 123 and sent to an adder 124. In the adder 124, the previous value latched by a latch circuit 125 is added to the variation amount output from the loop gain control multiplier 123 and the resulting value is sent to an operating section 126 via the latch circuit 125. The adder 124 and the latch circuit 125 composes an integration circuit and an integration value is latched by the latch circuit with the timing of a latch timing control value D. In the operating section 126, the integrating value is converted to data corresponding to the control voltage of the variable gain amplifier 111 and fed back to the control input end of the variable gain amplifier 111 as a gain control voltage. This realizes automatic gain control so that the output level of the variable gain amplifier 111 (output value of the level detector 114) may converge to a target value A.
Some types of radio communications apparatus that performs automatic gain control as mentioned earlier have receivers of a plurality of systems. In the related art, automatic gain controllers were provided as many as the number of receiving systems to correspond to receivers. That is, automatic gain controllers as shown in FIG. 11 were provided as many as the number of receiving systems and automatic gain control was individually performed in each receiver. In particular, it was necessary to provide an automatic gain controller for each receiver in order to obtain the optimum automatic gain control performance depending on the operating status in each receiving system.
In radio communications apparatus according to the related art having aforementioned receivers of a plurality of systems, as many automatic gain controllers as the number of receiving systems are provided. Thus, a plurality of automatic gain controllers were always operating, which causes a problem that the circuit scale and power consumption were increased. Power consumption of a circuit increases in proportion to the number of systems even if the automatic gain controller is configured by way of software design. Even if a single automatic gain control loop was used in common among a plurality of receiving systems in order to reduce power consumption, it was impossible to fully correct variations in the circuit characteristics such as the temperature characteristics and frequency characteristics of a variable gain amplifier of each system, thus the optimum automatic gain control performance was not obtained. In particular, in an unstable system state such as the power on or intermittent data reception, or in a bad receiving state, i.e., when variation in the receiving level is large or fading has taken place, high-accuracy automatic gain control is required. In the configuration according to the related art, a proper gain control signal is not obtained and desired automatic gain control cannot be performed.
The invention, in view of the aforementioned circumstances, aims at providing an automatic gain controller and an automatic gain control method wherein automatic gain control of a plurality of systems can be performed depending on the operating state such as the stable/unstable signal level and power consumption can be reduced, and to radio communications apparatus equipped with the automatic gain control function.
An automatic gain controller according to the invention is a automatic gain controller having variable gain amplifiers of a plurality of systems and the corresponding control loops, comprising: a gain control signal generator which generates a gain control signal that controls a variable gain amplifier based on the output signal level of the variable gain amplifier; a variation amount detector which detects the variation amount of the output signal level; a level comparator which compares the output signal levels of the plurality of system with each other; an inter-control-loop correction section which generates a correction gain control signal that corrects variations in the circuit characteristics of the other control loops and that is based on a gain control signal in the control loop where the output signal level is the highest in order to perform gain control, and an operation controller which selects the control loop where the output signal level is the highest, places gain control signal generator for the other control loops in the non-operating state, and performs gain control of the variable gain amplifiers of the plurality of systems via the gain control signal in the control loop where the output signal level is the highest and correction gain control signals in the other control loops, in case the variation amount in the output signal level is smaller than a predetermined value.
The operation controller preferably places in the operating state the gain control signal generator for the control loops of the plurality of systems and performs gain control of the variable gain amplifier via a gain control signal in each control loop, in case the variation amount in the output signal level is larger than the predetermined value.
Preferably, the operation controller operates the gain control signal generator for each control loop in a predetermined period during system startup from the non-operational state at power-on, to perform gain control of the variable gain amplifier. Or, the operation controller operates the gain control signal generator for each control loop until the variation amount in the output signal level falls within a predetermined value during system startup from the non-operational state at power-on, to perform gain control of the variable gain amplifier.
Preferably, the operation controller operates the gain control signal generator for each control loop in a predetermined period during system startup from the non-operational state assumed in case intermittent operation is performed, to perform gain control of the variable gain amplifier. Or, the operation controller operates the gain control signal generator for each control loop until the variation amount in the output signal level falls within a predetermined value during system startup from the non-operational state assumed in case intermittent operation is performed, to perform gain control of the variable gain amplifier.
An automatic gain control method according to the invention is an automatic gain control method using variable gain amplifiers of a plurality of systems and the corresponding control loops, comprises: a gain control signal generating step for generating a gain control signal that controls a variable gain amplifier based on the output signal level of the variable gain amplifier; a variation amount detecting step for detecting the variation amount of the output signal level; a level comparison step for comparing the output signal levels of the plurality of system with each other; an inter-control-loop correction step for generating a correction gain control signal that corrects variations in the circuit characteristics of the circuit characteristics of the other control loops and that is based on a gain control signal in the control loop where the output signal level is the highest in order to perform gain control; and an operation control step for selecting the control loop where the output signal level is the highest, placing gain control a signal generator for the other control loops in the non-operating state, and performing gain control of the variable gain amplifiers of the plurality of systems via the gain control signal in the control loop where the output signal level is the highest and correction gain control signals in the other control loops, in case the variation amount in the output signal level is smaller than a predetermined value.
The operation control step preferably places in the operating state the gain control signal generator for the control loops of the plurality of systems and performs gain control of the variable gain amplifier via a gain control signal in each control loop, in case the variation amount in the output signal level is larger than the predetermined value.
Preferably, the operation control step operates the gain control signal generator for each control loop in a predetermined period during system startup from the non-operational state at power-on, to perform gain control of the variable gain amplifier. Or, the operation control step operates the gain control signal generator for each control loop until the variation amount in the output signal level falls within a predetermined value during system startup from the non-operational state at power-on, to perform gain control of the variable gain amplifier.
Preferably, the operation control step operates the gain control signal generator for each control loop in a predetermined period during system startup from the non-operational state assumed in case intermittent operation is performed, to perform gain control of the variable gain amplifier. Or, the operation control step operates the gain control signal generator for each control loop until the variation amount in the output signal level falls within a predetermined value during system startup from the non-operational state assumed in case intermittent operation is performed, to perform gain control of the variable gain amplifier.
Radio communications apparatus according to the invention has receivers of a plurality of systems comprising a automatic gain controller according to any of the foregoing aspects of the invention, the radio communications apparatus performing automatic gain control for making constant the output signal level concerning a received signal via the automatic gain controller.
In the aforementioned configuration, a gain control signal is generated based on the output signal level of the variable gain amplifier in obtaining a constant output signal by variably amplifying input signals of a plurality of systems respectively via the variable gain amplifier, and the variation amount in the output signal level is detected. In case the variation amount in the output signal level is smaller than the predetermined value, the automatic gain controller selects the control loop where the output signal level is the highest, places gain control signal generator for the other control loops in the non-operating state, and performs gain control of the variable gain amplifiers of the plurality of systems via a gain control signal in the control loop where the output signal level is the highest and correction gain control signals in the other control loops, in case the variation amount in the output signal level is smaller than a predetermined value. In case the variation amount in the output signal level is larger than the predetermined value, the automatic gain controller places in the operating state the gain control signal generator for the control loops of the plurality of systems and performs gain control of the variable gain amplifier via a gain control signal in each control loop.
In case system operation is unstable and high-accuracy gain control is required such as in a predetermined period during system startup from the non-operational state at power-on, in a predetermined period during system startup from the non-operational state assumed in case intermittent operation is performed, and until the variation amount in the output signal level falls within a predetermined value during system startup from the non-operational state, the automatic gain controller operates the gain control signal generator for each control loop to perform gain control of the variable gain amplifier. Operation control made in case the intermittent operation is performed is preferably applied to a case where intermittent data reception is performed in radio communications apparatus.
In the aforementioned steady state, assuming the predetermined value for decision of switching operation between control loops as K1, the predetermined value for decision of switching operation at power-on, as K2, and the predetermined value for decision of switching operation in system startup in case intermittent operation is performed as K3, preferably K2 greater than K3 greater than K1 in order to upgrade the accuracy of detecting the variation amount in the output signal level or operation switching control.
Via the aforementioned operation control, it is possible to reduce the power consumption of a automatic gain controller while performing proper automatic gain control in a plurality of systems, by placing in the non-operating state part of the circuits such as the gain control signal generator of the automatic gain controller and correcting the other control loops based on the automatic gain control signal for a control loop where the output signal level is the highest, when the output signal level is stable. By applying an automatic gain controller and an automatic gain control method to radio communications apparatus, it is possible to reduce power consumption while securing good receiving performance, thus allowing long-duration operation.